INVITED REVIEW: IN VITRO CHILI PEPPER BIOTECHNOLOGY NEFTALI OCHOA-ALEJO 1 * and RAFAEL RAMIREZ-MALAGON 2 1 Departamento de IngenierõÂa Gene Âtica de Plantas, Unidad de BiotecnologõÂa e IngenierõÂa Gene Âtica de Plantas, Centro de Investigacio Ân y de Estudios Avanzados del Instituto Polite Âcnico Nacional (CINVESTAV-Unidad Irapuato), Apartado Postal 629, 36500-Irapuato, Gto., Me Âxico 2 Instituto de Ciencias Agrõ Âcolas, Universidad de Guanajuato, Apartado Postal 311, 36500-Irapuato Gto., Me Âxico (Received 17 May 2000; accepted 13 April 2001; editor G. C. Phillips) Summary Chili pepper is an important horticultural crop that can surely benefit from plant biotechnology. However, although it is a Solanaceous member, developments in plant cell, tissue, and organ culture, as well as on plant genetic transformation, have lagged far behind those achieved for other members of the same family, such as tobacco (Nicotiana tabacum), tomato (Lycopersicon esculentum), and potato (Solanum tuberosum), species frequently used as model systems because of their facility to regenerate organs and eventually whole plants in vitro, and also for their ability to be genetically engineered by the currently available transformation methods. Capsicum members have been shown to be recalcitrant to differentiation and plant regeneration under in vitro conditions, which in turn makes it very difficult or inefficient to apply recombinant DNA technologies via genetic transformation aimed at genetic improvement against pests and diseases. Some approaches, however, have made possible the regeneration of chili pepper plants from in vitro-cultured cells, tissues, and organs through organogenesis or embryogenesis. Anther culture has been successfully applied to obtain haploid and doubled- haploid plants. Organogenic systems have been used for in vitro micropropagation as well as for genetic transformation. Application of both tissue culture and genetic transformation techniques have led to the development of chili pepper plants more resistant to at least one type of virus. Cell and tissue cultures have been applied successfully to the selection of variant cells exhibiting increased resistance to abiotic stresses, but no plants exhibiting the selected traits have been regenerated. Production of capsaicinoids, the hot principle of chili pepper fruits, by cells and callus tissues has been another area of intense research. The advances, limitations, and applications of chili pepper biotechnology are discussed. Key words: Capsicum; plant regeneration; transformation; metabolite production; capsaicinoids. Introduction All chili peppers belong to the genus Capsicum of the Solanaceae family. Pepper, chili, chile, chilli, aji, paprika, and Capsicum are used interchangeably to describe the plants and fruits of the genus Capsicum (DeWitt and Bosland, 1993). There are 27 species of Capsicum, but only five have been domesticated and are currently cultivated: C. annuum Linne Â, C. baccatum Linne Â, C. chinense Jacquin, C. frutescens Linne Â, and C. pubescens Ruiz & Pavon. Barbara Pickersgill has proposed that the first varieties of chili peppers originated in the remote geologic past in an area bordered by mountains of southern Brazil to the east, by Bolivia to the west, and by Paraguay and northern Argentina to the south (DeWitt and Bosland, 1993). This location is called a nuclear area and has the greatest concentration of wild species of chili peppers in the world. The five major cultivated species are derived from different ancestral stocks found in three distinct centers of origin. Mexico is the primary center for C. annuum, with Guatemala a secondary center; Amazonia for C. chinense and C. frutescens; and Peru and Bolivia for C. baccatum and C. pubescens. Capsicum annuum and C. frutescens are widely distributed from Mexico through Central America and throughout the Caribbean region (Greenleaf, 1986). Capsicum annuum is the most extensively cultivated species in the world. It is the principal species grown in Hungary, Mexico, China, Korea and the East Indies. In Mexico, the spanish term chile refers to both hot and sweet types; therefore, chili pepper will be used interchangeably in this review to describe the plants and pods of the genus Capsicum. Because of the diversity of forms, colors, shapes, flavors, pungency and aromas, chili pepper fruits are important items worldwide as ingredients of a wide variety of dishes in many countries and also as salads, pickles, paprika, chili powder, curry powder, and pepper sauces. Chili peppers are the most used condiment and spice in the entire world, having dethroned black pepper (Andrews, 1995). Chili pepper fruits are among the most important commercially grown vegetables in the tropics, ranking only after tomato. They are exported to temperate countries in a dried form for use as a spice in flavoring sauces and processed foods. The world production of Capsicum fruits in 1998 was 701 In Vitro Cell. Dev. Biol.ÐPlant 37:701±729, November±December 2001 DOI:10.1079/IVP2001216 q 2001 Society for In Vitro Biology 1054-5476/01 $10.0010.00 *Author to whom correspondence should be addressed: Email nochoa@ ira.cinvestav.mx